Antonie van Leeuwenhoek is known for being the first to observe: MCQ with Answer and Explanation

Explanation:
Alexander Fleming, a Scottish bacteriologist, discovered penicillin in 1928. He returned from a vacation to find that a Petri dish containing Staphylococcus bacteria had been accidentally contaminated by a mold. He noticed a clear zone around the mold where the bacteria had been killed. The mold was identified as Penicillium notatum, and the antibacterial substance was named penicillin.

Explanation:
Polymerase chain reaction (PCR) amplifies a specific DNA segment exponentially using primers, DNA polymerase (Taq), and thermal cycling. Gel electrophoresis separates DNA by size, sequencing determines base order, microarray analyzes gene expression. PCR is crucial in cloning, diagnostics, and forensics.

Explanation:
Recombinant human insulin (Humulin) is produced by genetically engineered Escherichia coli (or yeast) carrying the human insulin gene. Before this, insulin from animal sources was used. The A and B chains of insulin are produced separately and then combined. This was the first genetically engineered pharmaceutical approved for human use (1982).